190 



ZOOLOGY, 



n 



the anterior part of the body of Linyula. The month is 

 bordered by two membranous, highly sensitive and movable 

 lips. The stomach is a simple dilatation of the alimentary 

 canal, into which empty the short ducts of the liver, which 



is composed of 

 masses of cooca. 

 The liver origi- 

 nally arises as 

 two diverticula 

 or offshoots of 

 the stomach. 

 The short in- 

 testine ends in 

 a blind sac or 

 in a vent, and 

 is, with the 



Linf/ula. m, mouth ; w. oesophagus ; ,/, stomach : a. arm ; ci, StomaC'h,fl"CCly 

 cirri ; iff. brachial 1'olcl ; cf>, cartilaginous base of arm ; , -i -i 



sinus leading to the arm ; cc, cephalic collar or pallial mem- SUSpenUCCl 1 11 



theperivisceral 



cavity by delicate membranes springing from the walls of the 

 body. (Fig. 129.) In those Brachiopods allied to Terebra- 

 tula, Tercbratulina, Thecidinm, Waldheimia, Rhynconetta, 

 etc., the stomach ends in a blind sac, and there is no vent, 

 the rejectamenta escaping from the mouth. In Lingula and 

 Discina there is a vent which terminates anteriorly on the 

 right side. In Lingula, 

 the intestine makes a 

 few turns, while in Dis- 

 cina it makes a single 



Fig. 128 Longitudinal section of the anterior portion of 



turn to the right. 



The nervous system 

 consists of two small 

 ganglia above, and an 

 infrao3sophageal pair of 

 larger ganglia, and there 

 are two elongated ganglia behind the arms, from which nerves 

 are given off to the dorsal or anterior lobe of the mantle. 

 From the infracesophageal ganglia two lateral ventral cords 

 pass backwards, in their tract sending off delicate threads, 



s 



Fig. 129. Transverse section of Lingnla, b, 

 bands suspending the intestine in the perivisce- 

 ral cavity ; i, intestine ; ., segments! organ ; o, 

 ovaries ;' I, liver ; y, gills ; ?, setre. After 

 Morse. 



